In 2025, water electrolysis for green hydrogen production continued to progress towards gigawatt-scale deployment worldwide, whereas CO₂ electrolysis for carbon-based fuels and chemicals synthesis saw advances at the cell and catalyst levels and moved towards pilot-scale demonstrations. Although at different stages of technical readiness, the two fields share common future challenges.
Key advances
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Water electrolysis reached new levels of scalability and durability in 2025. Alkaline seawater systems achieved stability beyond 10,000 h under intermittent conditions2, proton exchange membrane electrolysis achieved ~2 A cm−2 at ~2.0 V for 15,000 h with reduced iridium use1, and anion exchange membrane cells exceeded the US Department of Energy’s performance target of 2 A cm−2 at 1.7 V, although long-term stability remains limited.
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CO₂ electrolysis progressed from laboratory-scale breakthroughs to pilot-scale systems with improved selectivity and stability. C1 electrolysis (CO, formate) exceeded 80% Faradaic efficiency at industrial current densities5, C2+ products surpassed 80% Faradaic efficiency5, and engineering advances extended operational stability up to 4,500 h in pilot demonstrations6.
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The two technologies showed early convergence despite different maturity levels. Water electrolysis has been deployed at the megawatt to gigawatt scale, whereas CO₂ electrolysis entered the kilowatt to megawatt pilot stages, with both fields targeting improved stability, unified cell designs and renewable-compatible system integration.
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Acknowledgements
C.Z. acknowledges the financial support from the Australian Research Council (FL250100099, DP250101509, CE230100017 and IC200100023).
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Zhao, C., Li, H. & Li, F. Diverging maturity and converging challenges of water and CO₂ electrolysis in 2025. Nat. Rev. Clean Technol. 2, 8–10 (2026). https://doi.org/10.1038/s44359-025-00132-3
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DOI: https://doi.org/10.1038/s44359-025-00132-3
